Case Study

Round cell tumor of kidney and intrapelvic masses in a 7 year old MN Shepherd mix

A 7-year-old MN Shepherd Mix was presented for evaluation of tenesmus with no other obvious signs. On rectal palpation a mass on the ventral aspect of the lumbar spine that starts approximately 0.5 cm into the pelvic canal and extends cranial for about an inch

Sonographic Differential Diagnosis

Kidney Mass – the findings are severe -DDx: primary renal carcinoma, primary renal TCC, renal lymphosarcoma – may appear as diffuse disease or focal mass, renal malignant histiocytosis or mastocytosis, malignant osteosarcoma, hemangiosarcoma – metastatic VS. fungal infection (Cryptococcus or Aspergillosis).

Pelvic canal mass- the findings are severe-DDx: Benign vs. Neoplasia (primary vs. metastatic).

Lymph nodes – the findings are severe – DDx: infiltrative neoplasia (lymphoma vs. mast cell vs. other) vs. IBD vs. infection vs. reaction vs. metastatic neoplasia.

Image Interpretation

Left Kidney: Two cortical masses that are abnormally shaped and deforming the capsule measuring 14.1mm and 11.6mm and having heterogeneous hypoechoic echogenicity are visualized. Right Kidney: Normal size and shape with normal corticomedullary dimensions. Probable right and left medial iliac lymph node involvement associated with the pelvic canal/abdominal mass. They are increased in size, abnormally shaped, and have hypoechoic echogenicity, but hard to discern from the mass. A large irregularly shaped mass measuring ~61 x 34mm having heterogeneous hypoechoic echogenicity is seen in the caudal abdomen extending into the pelvic canal.

DX

Renal and intrapelvic masses-round cell tumor

Comments

Case courtesy of Marty Henderson, DVM – SonoVet, Inc.

Clinical Differential Diagnosis

Neoplasia, cyst, granuloma, abscess, lymph node

Sampling

FNA revealed a pelvic mass and renal masses – Poorly-differentiated, individually-exfoliating malignant round cells with melanin in the cytoplasm of many of the tumor cells, confirming that this tumor is a poorly-melanotic melanosarcoma; it is very possible that both these sites represent metastasis from an unknown primary tumor.